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To preserve battery life, double tap home button and close all the apps that have been running in the background sucking down precious electricity.

Sorry, that's 99% myth. Very few applications are permitted to run in the background, and most of the apps there are either just resident in memory, or not even that and just shown as recent applications.

There is a small sliver of truth to this myth, which is why it is hard to kill entirely. There is a very small subset of applications that run in the background, and if one of them malfunctions, it can drag down battery. Apple's bundled apps can execute in the background in some cases, but quitting them doesn't change anything. Anything playing audio in the background falls under this. Turn-by-turn GPS applications are notorious for this, as they use the navigation software, which draws down the battery quickly.

In any case, don't go quitting apps if you don't have a problem. If you are suddenly losing battery power more than usual, it might be worth looking in to if some app has malfunctioned, but just "cleaning up" the list of recently used apps doesn't help any.

The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.

To preserve battery life, double tap home button and close all the apps that have been running in the background sucking down precious electricity.

Please to to whomever told you this and slam them upside the head hard enough to make them unable to perpetuate this bullshit.

More or less, here's the (simplified) deal:

There are five use-cases for apps in the background: newsstand apps downloading new issues, VOIP, media players, navigation (though graphics are suspended), and apps downloading/uploading data (they can request ten minutes extra background time before they are killed).

All other apps are suspended after five seconds of being in the background (they can use this time to clean up and save state), and the RAM they use is immediately released when another app requests it.

Removing them from the list of used apps (that's basically what it is, in order of last use) does nothing at all.

Steve Jobs was serious about people not needing to use a task manager on iOS devices.